The present invention relates to an apparatus for detecting the coordinate positions of points on a plane, and in particular, to an apparatus comprising a movable cursor and a coordinate read device having an array of position-measuring conductors disposed on a plane for detecting by the conductors the alternate-current (AC) magnetic field generated by the cursor, thereby determining the position of the cursor.
Apparatuses for measuring a coordinate position have been described in the JP-B-57-31188, JP-B-53-34855, U.S. Pat. Nos. 3,735,044, and 3,647,963.
The JP-B-57-31188 and JP-B-53-34855 disclose apparatuses which require many position measuring conductors when the range of the coordinates to be read is great. The apparatuses of the U.S. Pat. Nos. 3,735,044 and 3,647,963 are suitable for an apparatus of which the coordinate read range is small, namely, these inventions are not suitably applicable to an apparatus having a large coordinate range to be read.